What you were expecting to happen, and what actually happened:
Last week on jul 15th I opened a glory chest and got my second lord of slaughter. I thought that mythics just released weren’t supposed to be available in chests for 28 days after release, but this was right after his 1 week exclusive period.
How often does this happen? When did it begin happening?
Just once July 15th
Key dropped mythics are gem/glory/vip chests immediately after their exclusive period ends. I mean, in addition to them obviously being in chests during their exclusive period… so they never actually leave these chests except during other mythics exclusive periods. Not sure if they are in event chests immediately on release, a week after, or two weeks after if that set of circumstances happens to align.